Screw compressors are widely used in refrigeration and other environments, and involve screw rotors rotated within a housing or casing to compress refrigerant to obtain the desired objectives. Excessive clearance between screw rotors and the housing results in loss of efficiency, while insufficient clearance results in rubbing and potential failures due to scoring or excessive wear of compressor components.
Ideally, screw compressors would be provided having clearance of zero or as close to zero as possible along the entire rotor length, for all operating conditions of the compressor. Of course, it is impossible to achieve such zero clearance as different operating conditions subject the compressor to different stresses and forces which cause the clearance to vary across the rotor length.
The primary object of the present invention is to modify screw compressor design to reduce clearance along the rotor length and/or reduce clearance variations due to changes in operating conditions, particularly within an expected operating envelope, without compromising compressor reliability.
If clearance variations during compressor operation are reduced, then the compressor can be assembled having smaller clearances, while maintaining rub free operation throughout the operating envelope. It is a particular objective of the present invention to provide such reduction in clearance variations.
Other objects and advantages of the present invention will appear hereinbelow.